Borehole orientation tool

ABSTRACT

The particular embodiment described herein as illustrative of one form of the invention utilizes a device for detecting the angular position and directional orientation of a housing within a wellbore and for generating a signal indicative of such information for transmission to the earth&#39;&#39;s surface.

I Umted States Patent [191 (111 3,771,118 Lichte, Jr. et al. Nov. 6,1973 BOREHOLE ORIENTATION TOOL 2,305,999 12/1944 Boucher 33/2052,438,293 3/l948 Livingston [75] lnvmmrs- Hen"? meme 3,180,034 4/1965McDonnell 33 205 Lindsey, both of Houston, Tex.

[ Assigncci p y- Surveying Primary ExaminerBenjarnin A. Borchelt Comp y,S g a Tex. Assistant Examiner-H. A. Birmiel Aztarne -Geor e L. ChurchDonald R. Johnson 22 F l J g l 1 led Nov 1969 Wilmer E. McCorquodale,Jr. and John E. Holder [2i] Appl. No.: 879,009

[57] ABSTRACT [52] [1.8. CI. 340/18 R, 33/308, 33/312 51 Int. Cl. 1521b47/022, GOlc 9/00 The P embdlmem Embed as [58] Field 0 Search 340/1833/205 trative of one form of the invention utilizes a device for 33/304308 detecting the angular position and directional orientation of ahousing within a wellbore and for generating {56] References Cited asignal indicative of such information for transmission to the earth ssurface.

10 Chims, 4 Drawing Figures PATENTEW 6 I91: 3771.118 SHEET 1 BF 2 PULSEGENERATOR T l 4 s l a W a 10 0 E 0 1* PENDULUM PENDULUM T '3 I gFLIP-FLOP I09 \07 GATE l4 IGVI 1 E PENDULUM PENDULUM v 2 2 FLIP-FLOPGATE 2 '8 T H GYRO GYRO A FLIP- FLOP l9 GATE 3 23A DATA DATA COUNTER a EPROCESSING STORAGE 24% UNIT G PROCESSED DATA FIG 4 RECORDTNG INVENTORSHENRY P LICHTE, JR JAMES M, LINDSEY ATTORNEY PMENTEUHUY 6 ms 3.771.118

SHEET 2 OF 2 FIG. 2 FIG. 3

INVENTORS HENRY I LICHTE, JR.

MES M. LINDSEY ATTORNEY BOREI'IOLE ORIENTATION TOOL BACKGROUND OF THEINVENTION This invention relates to a position sensing device, and moreparticularly, to an apparatus for sensing the position of an object andproviding an electrical signal indicative of the attitude of suchobject. During the drilling of boreholes in the earth formation, it isoften desirable to determine the attitude of the hole, not only at thebottom of the hole, but throughout its traverse of earth formations. Itis for this reason that various apparatus and methods have been devisedfor making such determinations of borehole attitude. Normally suchsystems consist of apparatus for measuring the angular disposition ofthe hole with respect to some reference such as a horizontal referenceplane, and in addition, means for determining the direction of the holewith respect to a reference such as Magnetic North. A typical apparatusfor making such determinations of a borehole position consists of aninstrument unit, including a compass or a gyro, together with an angularunit having a plumb-bob arrangement, and a photographic device of somesort for making a photographic recording of the instruments in thewellbore. In the past, these instruments have been run on wirelines orgodeviled into the drill pipe, where they are subsequently retrieved asin the latter case, by removing the drill pipe from the borehole. Uponretrieval of the instrument to the surface, the photographic equipmentis removed and the exposed film record of the instrument recordings isthen removed to a suitable location for developing the film. Thereafter,if calculations are to be made regarding the orientation of theborehole, such information derived from the film can then be utilized incomputation equipment for making such determinations. In any event, theprocedure outlined above is time consuming, and if decisions forcontinuing drilling or for making changes in the orientation of thewellbore are required, then such decisions must be held in abeyanceuntil the film is developed and computations can be made from theindicated parameters of the well borehole.

It is therefore an object of the present invention to provide a new andimproved apparatus for determining the positional orientation of anobject.

SUMMARY OF THE INVENTION With this and other objects in view, thepresent invention contemplates an instrument for use in a boreholewithin the earth for detecting and sending signals to the surfaceindicative of the orientation of the apparatus within the borehole.

The device may be comprised of separate units for detecting differentparameters of orientation. The units are comprised of a scanning deviceand means actuable in response to the scanning device for sending afirst signal to an electronic section indicative of a reference positionon the apparatus relative to the apparatus housing. A second signal issent to the electronic section and is indicative of the position of amember within the aparatus housing in turn which is determinative of apositional parameter of the housing within the borehole. The scanningmeans is time pulsed so that it may be determined, by counting suchpulses between the first and second signals, what the angular differenceis between the first and second signals. This angular difference may betranslated into terms of degrees of direction or degrees of angulardeviation. A signal is transmitted from the electronic section to thesurface, which signal carries information indicative of direction andangular deviation.

A complete understanding of this invention may be had by reference tothe following detailed description, when considered in conjunction withthe accompanying drawings illustrating embodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of awellbore tool including instruments for measuring angular and azimuthalparametrs of the tool position;

FIG. 2 is a partial cross-sectional view of a wellbore instrument formeasuring the angular orientation of the instrument within the wellbore;

FIG. 3 is a partial cross-sectional view of a wellbore instrument formeasuring the directional orientation of the instrument within thewellbore; and

FIG. 4 is a schematic drawing of a system for transmitting wellboreinstrument data to the surface.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus described hereinis provided in a borehole tool for detecting positional parameters of aninstrument within a borehole, and transmitting such data to the surfacewhere it is processed and recorded in a form permitting a directread-out of borehole orientation date. The apparatus forming thisinvention includes the downhole units for detecting such positionalorientation and for providing data to the surface indicative of suchinformation.

FIG. 1 shows a schematic of such a wellbore tool which includes an angledetecting section 12 having first and second angle detecting units 13and 14 mounted therein to measure the angular disposition of planes insection 12 which are to one another. A synchronous motor 16 ispositioned between the units to provide a source of power for drivingscanning systems within the units to thereby monitor parameters of thedetecting units which are indicative of their angular disposition. Themotor 16 has output shafts extending upwardly and downwardly therefromto drive the respective scanning systems for the first and second units13 and 14. A directional section 17 is positioned below the angledetecting section and includes mechanisms for measuring the directionalorientation of the housing relative to the earth's surface. Thedirectional section 17 incorporates a gyroscope 18, a gyro motor 19, andan encoder 21 for providing a reference signal to the detecting units. Alower section 22 houses a gyro torque motor 23 and a torque motorcircuit 24 for controlling precessing of the gyro. An upper electronicsection 26 of the tool houses an electronic scanner circuit and datacounter and storage units.

An angle detecting unit 13, 14 for generating signals indicative of theangular position of the instrument within the borehole is shown indetail in FIG. 2 of the drawings. The angle unit includes a partiallyenclosed housing 27, having the synchronous motor 16 mounted at itsupper end. The motor has an output shaft driven at 3600 rpm. Between thesynchronous motor and housing is mounted a transmission or gearreduction section 29 which has two stages of pinion gears connected withthe output shaft 28 of the synchronous motor for reducing the outputrevolution thereof. The

output of the gear reduction section is fed through a shaft 31 whichextends longitudinally from the upper to the lower end of the instrumenthousing. At the lower end of the output shaft, a worm gear 32 is rotatedtherewith for driving a spiroid gear 33, which in turn drives a scanningsystem within the instrument. The total gear reduction between theoutput of the synchronous motor and the rotation of the spiroid gearwithin the instrument housing is from 3600 rpm of the motor to rpm ofthe spiroid gear 33.

The angle detector and scanning system are located within the housingand include a horizontal shaft 36 extending transversely across thehousing midway between its ends. A scanner assembly is rotatably mountedabout the left side of the shaft as viewed in FIG. 2, and is providedwith bearings 37, 38 for rotatably supporting the assembly about theshaft. The scanner assembly is comprised of a large diameter verticaldisc 39 upon one side of which is mounted the circular spiroid gearsection 33. The spiroid gear is arranged to mesh with the worn gear 32on the shaft 31 extending vertically through the housing. A sleeve 41extends outwardly from the vertical disc 39, and is positioned about thehorizontal shaft 36. An insulating cylinder 42 is positioned about thesleeve. Grooved commutator rings 43 are positioned about the insulator.The grooved commutators are electrically insulated from one another toprovide separate electrical flow paths between the stationary portion ofthe instrument housing and the rotating scanner section. An insulatingpost 44 is positioned above the commutators and is connected to the sidewall of the housing. Brushes 46 extend downwardly from the post intocontact with the commutators. The upper ends of the brushes areconnected to terminal posts 47 to provide a means for electricallyconnecting the brushes with conductor wires (not shown) within theinstrument housing.

Referring again to the vertical disc 39 of the scanner section, a lamp48 and lamp housing 49 are shown extending outwardly from the outer rimof disc 39 toward the center of the housing. A first slit 51 is formedin the outer wall of the lamp housing and is perpendicular to the shaft36. A second slit 52 is formed along the bottom portion of the lamphousing 49 and is parallel with the shaft 36. A detector photocell 53and housing 54 are mounted on the disc 39 and extend outwardly from thedisc on the same side as the lamp 48 and housing 49. Wires (no shown)extend from the photocell through the disc and into contact with thecommutator rings. The photocell housing has a slit or opening 56 in itsupper side wall and parallel to the shaft 36 to permit light emanatingfrom lamp 48 to project into the housing for activating the photocell.Conductor wires are also provided to the lamp housing from thecommutator rings to provide an electrical power source to the lamp.

A pendulum assembly is also mounted on the horizontal shaft 36 oppositethe scanner assembly. The pendulum assembly is comprised of an annularsleeve 57 positioned about the shaft and rotatably supported thereon bymeans of bearings at each end of the annular sleeve. A circular shield58 extends outwardly from the sleeve and includes an L-shaped endportion 59 extending inwardly therefrom toward the circular disc 39 ofthe scanner section. The inwardly extending portion 59 of the shieldapproaches contact with the vertically mounted disc 36, but does notcontact the disc, so that the pendulum assembly is free to moveindependently with respect to the scanner assembly. The shield and itsinwardly extending portion are arranged to pass over and about thedetector photocell 53 and housing 54. The inwardly extending portion ofthe shield passes between the bottom of the lamp housing 49 and theupper side of the photocell detector housing 54. A slit 61 is formed inthe inwardly extending portion of the sleeve in parallel relationshipwith the slit 52 formed in the lower side of the lamp housing. Aweighted pendulum member 63 is connected to the shield 58 and covers apartial segment of the shield. This weighted pendulum member maintainsthe shield in an oriented position relative to gravity, regardless ofthe position of the housing with respect to gravity, since the pendulumassembly is freely mounted for rotation upon the horizontal shaft 36.The slit 61 is in the inwardly extending portion 59 of the shield ispositioned at a point thereon corresponding to a point on the peripheryof the weighted pendulum member 63 directly below the center of gravityof the weighted member when the member is at free rest relative togravity.

Also mounted within the interior of the housing is a second or referencephotocell or other such light sensitive device 64, which is positionedat the upper end of the interior portion of the instrument housingopposite a point on the path of movement of the lamp 48. A vertical slit66 is provided within the outer wall of a photocell housing 67, whichslit is arranged to be oppositely disposed and parallel to the slit 51in the lamp housing 49. Conductor wires (not shown) provide anelectrical power source for the photocell 64.

In the operation of the apparatus justdescribed, the synchronous motor16 is continuously driving the gear reducing mechamism to rotate thespiroid gear 33 and scanner disc at a rate of 20 resolutions per minuteor 1 revolution every 3 seconds. This means that the lamp 48 on thescanner disc 39 will pass in front of the reference photocell 64 on theinterior wall of the housing, once every three seconds. The lamp 48 iscontinuously energized. As a result, the reference photocell will beactivated to generate a signal once every three seconds for purposes tobe hereinafter described.

As the scanner disc and lamp continue to rotate during each revolution,a second signal is generated when the lamp 48 passes the slit 61 in theinwardly extending portion of the pendulum shield. The slit 61 permitslight from the lamp to impinge upon the detector photocell 53 which ispositioned on the scanner disc 39 next to the lamp 48. The shieldnormally prevents the lamp from activating the photocell 53, except whenthe lamp and photocell pass the slit 61 in the pendulum once during eachrevolution of the disc. The slit in the shield is positioned relative tothe gravitational pull of the weighted pendulum member, so that eventhough the housing is tilted at an angle with respect to the vertical,the shield will remain in a constant position determined by the force ofgravity. Therefore, the slit 61 in the shield will always remain at thebottom (relative to earth's gravity) of the pendulous shield. As thelamp 48 and photo detector cell 53, which are mounted on the scannerdisc move past the slit 61 in the pendulum shield at its lower side, thelight emanating from the lamp will pass through the slit and beprojected upon the detector photocell, which in turn generates a signalthat is picked up from the commutator rings and brushes for purposes tobe hereinafter described.

It is readily seen that as the scanning disc 39 rotates, a pulse isgenerated once every three seconds by the case reference photocell 64,and that a second pulse is generated at some time lapse after the firstcase reference photocell pulse is generated, depending upon the positionof the slit 61 in the pendulum shield relative to the case referencephotocell. If, for example, the instrument housing were lying in ahorizontal position with respect to the surface of the earth, thescanner, if operating in a clockwise direction, (as viewed from theright side as shown in FIG. 2) would generate a first signal when thelamp 48 passes the slit 66 in the case reference photocell housing. 90rotational degrees thereafter, the scanner would generate a secondsignal when the lamp 48 passes the slit 61 in the pendulum shield toactivate photocell 53. If the time rate of rotation of the scanning disc39 is known, then the actual number of degrees transgressed by thescanning mechanism between such first and second signals may becalculated.

In order to provide completely accurate information as to the angularposition of the instrument housing with respect to a vertical referenceplane, it is desirable to utilize a second angle detecting unit 14,which is mounted so that the scanning disc and pendulum shield of thesecond instrument are in a vertical plane perpendicular to that of theplane of the shield and disc in the first instance. As will be describedhereinafter, the data outputs of each of the pendulum instrumentsections is fed to a data processing unit where a vector summation ofthe outputs provides a true calculation of the angular disposition ofthe instrument housing.

Referring now to FIG. 3 of the drawings, details of the directional unit17 (FIG. 1) are shown. Directional unit 17 provides information relativeto the directional or azimuthal orientation of the instrument housing.The unit shown in FIG. 3 is very similar to that of FIG. 2 in that ascanning section is rotated relative to a shield, which instead of beingoriented by a pendulum, is driven by the rotation of the vertical shaft71 of the directional gyroscope 18. The vertical or output shaft 71 ofthe gyroscope is shown connected to a vertical sleeve 73, which is pressfitted onto the output shaft of the gyro. The sleeve has an outwardlyextending shield portion 74 which in turn has an upwardly extendingcircular shield wall 76. The gyro instrument housing 77 has synchronousmotor 19 and gear reduction section 79 mounted on its upper side, withthe output shaft 81 of the gear section extending through the top of theinstrument housing 77 and downwardly into the instrument. Bearings areprovided in the top of the instrument housing to rotatably support themotor driven output shaft. A scanning section is mounted on the motordriven output shaft for rotation within the instrument housing. Thescanner section is comprised of a vertical sleeve 82 attached to thelower end of the shaft. The sleeve has an insulated cylinder 83 aboutits outer walls upon which are mounted commutator rings 84 which areelectrically insulated from one another. At the lower end of the scannersleeve, a horizontally disposed circular disc or plate 86 is shownextending outwardly therefrom. A scanning lamp 87 is attached to thelower side of the circular disc near its outer rim and extendsdownwardly therefrom. A detector photo- I cell 88 is also attached tothe under side of the disc and i of the housing, and a second verticalslit 93 on the inner wall of the lamp housing. The upwardly extendingvertical wall 76 of the shield is positioned between the scanning lamp87 and detector photocell 88 mounted on the scanning disc. A slit 95 isformed in the vertical wall of the shields. A case reference photo cell94 is mounted within a housing 96 upon the inner wall of the instrumenthousing in a spaced relation with the outer rim of the scanner disc andthe lamp 87. Clearance is provided between the reference photocellhousing 96 and the lamp housing 91. A slit 97 is provided in the topside of the case reference photocell housing to permit light emanatingfrom the lamp housing to impinge upon the photocell 94.

An insulating block 98 is shown extending downwardly from the upper endof the instrument housing. The block holds horizontally disposed brushes99 therein for contacting commutator rings 100 on the scanning sleeve.Terminals 101 are connected to the brushes to provide electrical contactwith conducting wires (not shown) for supplying electrical power to thelamp and for transmitting a signal from the detector photocell toelectrical circuitry within the instrument. Likewise, suitable conductorwires are connected with the case reference photocell to provide a meansfor transmitting a signal therefrom to such electrical circuitry withinthe instrument housing.

A shaft 102 also extends upwardly from the motor 19 of the instrumentfor driving an encoder 21. The output shaft from the motor is rotated at3,600 rpm, or 60 revolutions per second. The encoder is arranged to berun from the output shaft of the motor and to multiply such rotation ofthe output shaft as to provide 12,000 pulses per second from theencoder.

The gear reduction section 79 is placed between the output shaft of themotor and the scanning device in the instrument housing so that thescanner is operated at 20 rpm or I revolution every 3 seconds.Therefore, when the scanning mechanism has made I revolution within theinstrument housing, in three seconds, the encoder or pulse generator hasproduced 36,000 pulses. As will be described later, this relationshipbetween the encoder pulses and the scanner rotation readily permits adetermination of degrees of scanner rotation between signals from thefirst and second photocells to an accuracy of 0.01. It is also seen thatsynchronization between the scanning mechanism in the instrument and thepulses generated by the encoder prevents any variation in the powersupply from effecting the readout. Any variation in the operation of themotor from its intended 3,600 rpm will provide a proportionalrelationship between the rotational speed of the scanner and the outputpulses from the pulse generator. The motor driving the angle detectingunits is driven synchronously with motor 19 and encoder pulses fromencoder 121 are also provided to circuitry for reading the angle units.

Referring next to FIG. 4 of the drawings, a schematic representation ofan electrical system for utilizing the information derived from theangle and azimuth units is shown. The pendulum l and 2 angle detectingunits 13, 14 respectively and the gyro instrument section are shownhaving output lines leading to respective flip flop circuits. Forexample, the first output 104 of the pendulum 1 unit represents thescanning signal derived from the case reference photocell. This casereference signal places a pendulum I flip flop circuit 106 in conditionto conduct and thus privide an output signal 107 through a conductor toan associated AND gate circuit 108, which is labeled Gate 1. A secondsignal output 109 from the pendulum l scanning section represents asignal derived from the detector photocell 53. The circuit is arrangedso that this detector signal causes the pendulum l flip flop 106 tocease operation which in turn stops the flip flop output signal 107 toGate 1.

During operation of the flip flop by the scanning signals, pulses fromthe pulse generator or encoder 21 are fed at the rate of 12,000 pulsesper second to the Gates 1, 2, and 3 of pendulum l, 2, and the gyrorespectively. When the respective flip flops are operating, pulses fromthe pulse generator will be counted or passed by the gate to a datacounter and storage unit 1 l 1. When the flip flop ceases to operate,the gate discontinues passage of the pulses from the pulse generator tothe date counter. Therefore, the duration of the signals from the flipflops will determine the time that such pulses are passed through thegate circuits to the data counter.

Referring again to the pendulum l instrument, when the scanning lamppasses the case reference photocell, the pendulum I flip flop isactivated, which in turn sends the output signal 107 to Gate 1. Thisoutput 107 opens Gate 1 to permit the passage of pulses generated by thepulse generator to the data counter and storage unit. Such a signal fromthe flip flop will continue until the lamp 48 on the scanner passes theslit 61 in the pendulum shield to generate signal output 109 from thedetector photocell 53. The output 109 will cause operation of flip flop106 to cease and thereby close Gate 108. The Gate will thus ceasepassing the pulses generated by the pulse generator to the date counter.For example, if the scanner lamp 48 takes 1 A seconds to move from thereference photocell to the detector photocell, the flip flop will beoutputting a signal for 1 A seconds. During this time span, 18,000pulses from the pulse generator will be passed by the pendulum l gate tothe data counter. Since the scanner rotates at a rate of one revolutionevery three seconds, the scanner will have moved in the 1 Va secondsover an arc of 180.00", thus the detector photocell is located 180 fromthe reference photocell. This indicates that the detector housing is ina vertical position, and that therefore the wellbore is in a verticallyoriented position, since the slit 66 in the reference photocell, whichis at the top of the housing is, in fact, 180 away from the slit 61 inthe pendulum shield which is located at the bottom center of thependulum.

Operation of the gyro unit in the instrument is similar to thatdescribed above with respect to the pendulum units. The referencephotocell on the azimuth unit is photocell 88. The slit 95 which permitslight from lamp 87 to impinge upon photocell 88 is oriented with respectto the tool housing and one of the pendulum units which in turn isoriented with respect to magnetic North at the earth's surface. Whilethe gyro unit housing turns in the wellbore, the gyro and slit 95 remainoriented with respect to magnetic North. Thusq when Thus, scanner lamp87 passes the slit 95 the associated flip flop begins to conduct untilthe scanner lamp passes slit 97 to operate photocell 94. Ths pulsespassed by gate 3 during this time span are likewise indicative ofazimuthal degrees of difference between magnetic North and the referencephotocell 94 on the gyro unit housing. Since the gyro unit is referencedto the pendulum units and magnetic North, the readings from these unitsmay be combined to give a true angular and azimuthal orientation of thetool housing. First the outputs of the angle units are summedvectorially to provide an angle of inclination of the housing. Then, ifthe gyro unit output indicates that the housing has rotated X degreesfrom North, the pendulums have moved the same amount and the vectorsummation is likewise rotated X degrees. The resultant computation givesthe angular disposition of the housing relative to magnetic North orsimilar surface reference.

The pulses which are supplied to the data counter from the surface unitsare stored in the counter and storage unit in binary form. After theinformation is read out of the pendulum l gate into the counter andstorage unit, a switch causes information from the pendulum 2 gate topass into the data counter and storage unit in the same manner, andlikewise with the gyro unit. This information in turn is fed into thedata processing unit at the surface, where the information relative tothe pendulum l and pendulum 2 positions is used to calculate the angulardisposition of the pendulums by performing a vector summation of thevalues supplied by each of the units which are located to one another inthe instrument housing. The gyro information is then combined with suchangular information to provide data which will be indicative of theorientation of the tool, and therefore the borehole. This informationmay then be printed out in any wellknown manner or recorded for futureuse.

The data counter and storage unit consists of three sixteen bit, countand store units. By using counting and storage units, or "clock gatedflip flops" as they are called, information may be read out from thestorage units, while new information is gathered from the scanningsystems into the counting units. Thus, the information in the storageunits is continuously up dated, and is always available for immediateread out. The pendulum and gyro units are continuously scanned at aonesecond scan rate, and the information stored in individual storageracks. These storage racks are scanned electronically by using a 16 bitring counter driven by an oscillator or line frequency. A second threebit ring counter is driven from the sixteen bit ring, and is used as agateing programmer to select the storage register to be read out. The 48bits of information from the three storage registers is read out instraight serial binary form, in one-second intervals, and sent to thesurface on a single conductor line. The power to the in strument is fedover the same conductor and may be either AC or DC voltage.

Alternatively, a multiple conductor cable may be used to pass signalsfrom the gates l, 2, and 3 directly to the surface where they may bestored and processed in much the same manner as described above.Although described with respect to surface recording, it is readily seenthat the apparatus described herein would be compatible for use withdownhole recording equipment.

While particular embodiments of the present invention have been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspects, and theaim in the above description is to cover all such changes andmodifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

l. A wellbore apparatus including a housing and having means formeasuring a parameter of the positional attitude of the housing in thewellbore, which means comprises: a surface oriented member mounted formovement in said housing; means on said surface oriented member forproviding a first reference marker indicative of the position of saidmember; means on said housing for providing a second reference markerindicative of a parameter of the attitude of said housing; means forcyclically scanning said first and second reference markers and forgenerating periodic signals indicative of the relative positions of saidfirst and second reference markers, said reference markers and scanningmeans including a light source, light admitting means, and lightsensitive means for providing an electrical signal in response tomovement to said light source past said light admitting means; and apulse source and a pulse counter wherein said light sensitive meansprovides a first gate signal in response to the movement of said lightsource past said first reference marker for starting the pulse counterand a second gate signal in response to the movement of said lightsource past said second reference marker for stopping the pulse counter.

2. A system for detecting and indicating the positional attitude of anapparatus within a wellbore comprising: a housing having first andsecond instrument means for detecting the angular attitude of saidhousing; said first and second instrument means each having a pendulousmember oriented with the earth's surface and a reference marker on saidhousing; cyclic scanning means for detecting the position of saidpendulous member and said reference marker during each scanning cycle;and means for providing electrical gate signals in timed proportion tothe angular distance between the pendulous member and said referencemarker.

3. The apparatus of claim 2 wherein said scanning means includes lightsource means, and light sensitive means for detecting changes in theposition of said pendulous member.

4. The apparatus of claim 2 and further including a third instrumentmeans having an azimuth oriented member and an azimuth reference marker,cyclic scanning means for detecting the position of said azimuthoriented member and said azimuth reference marker during each scanningcycle, and means for providing electrical gate signals in timedproportion to the angular distance between the azimuth oriented memberand the azimuth reference marker.

5. The apparatus of claim 4 and further including means for counting thetimed relation between said gate signals and for storing informationindicative of such timed relation.

6. The apparatus of claim 5 and further including means for providingpulses in multiples of 36 for each scanning cycle wherein said gatesignals start and stop the passage of said pulses to said countingmeans.

7. The apparatus of claim 5 and further including means for combiningthe information derived from said instrument means for providingaccurate measurements of the attitude of said housing with respect tothe earth's surface.

8. In a position sensing and indicating system for determining theorientation of a borehole: a housing arranged for suspension in aborehole on a cable; a first angle detecting unit in said housing fordetecting the angular disposition of said housing in a first plane; asecond angle detecting unit in said housing for detecting the angulardisposition of said housing in a second plane perpendicular to saidfirst plane; electrical means for scanning each of said units todetermine the angular disposition of such respective units relative to afixed reference and for generating output signals indicative of theangular relationship between the disposition of such units and the fixedreference; and means for electrically receiving and storing said outputsignals to make subsequent calculations based thereon determinative ofthe orientation of said housing and borehole in relation to the earthssurface.

9. A method of determining the positional attitude of a boreholecomprising the steps of: passing an instrument housing into the boreholeon a single conductor cable; measuring a parameter of the inclination ofsuch housing in a first plane; measuring a parameter of the inclinationof such housing in a second plane; detecting a parameter of thedirection of inclination of such housing in a borehole; providingsignals indicative of such parameters to the earth's surface over thesingle conductor cable; combining the parameters of inclina tion inrelation to the planes of measurement; and applying such parameter ofdirection to the combined parameters of inclination to determine thetrue positional attitude of such borehole.

10. The method of claim 9 and further including the steps of providingpulses in timed proportion to the measured parameters. counting suchpulses, storing data indicative of such counted pulses, and transmittingsuch stored data to the surface prior to combining and applying suchparameters.

t t i t t

1. A wellbore apparatus including a housing and having means formeasuring a parameter of the positional attitude of the housing in thewellbore, which means comprises: a surface oriented member mounted formovement in said housing; means on said surface oriented member forproviding a first reference marker indicative of the position of saidmember; means on said housing for providing a second reference markerindicative of a parameter of the attitude of said housing; means forcyclically scanning said first and second reference markers and forgenerating periodic signals indicative of the relative positions of saidfirst and second reference markers, said reference markers and scanningmeans including a light source, light admitting means, and lightsensitive means for providing an electrical signal in response tomovement to said light source past said light admitting means; and apulse source and a pulse counter wherein said light sensitive meansprovides a first gate signal in response to the movement of said lightsource past said first reference marker for starting the pulse counterand a second gate signal in response to the movement of said lightsource past said second reference marker for stopping the pulse counter.2. A system for detecting and indicating the positional attitude of anapparatus within a wellbore comprising: a housing having first andsecond instrument means for detecting the angular attitude of saidhousing; said first and second instrument means each having a pendulousmember oriented with the earth''s surface and a reference marker on saidhousing; cyclic scanning means for detecting the position of saidpendulous member and said reference marker during each scanning cycle;and means for providing electrical gate signals in timed proportion tothe angular distance between the pendulous member and said referencemarker.
 3. The apparatus of claim 2 wherein said scanning means includeslight source means, and light sensitive means for detecting changes inthe position of said pendulous member.
 4. The apparatus of claim 2 andfurther including a third instrument means having an azimuth orientedmember and an azimuth reference marker, cyclic scanning means fordetecting the position of said azimuth oriented member and said azimuthreference marker during each scanning cycle, and means for providingelectrical gate signals in timed proportion to the angular distancebetween the azimuth oriented member and the azimuth reference marker. 5.The apparatus of claim 4 and further including means for counting thetimed relation between said gate signals and for storing informationindicative of such timed relation.
 6. The apparatus of claim 5 andfurther including means for providing pulses in multiples of 36 for eachScanning cycle wherein said gate signals start and stop the passage ofsaid pulses to said counting means.
 7. The apparatus of claim 5 andfurther including means for combining the information derived from saidinstrument means for providing accurate measurements of the attitude ofsaid housing with respect to the earth''s surface.
 8. In a positionsensing and indicating system for determining the orientation of aborehole: a housing arranged for suspension in a borehole on a cable; afirst angle detecting unit in said housing for detecting the angulardisposition of said housing in a first plane; a second angle detectingunit in said housing for detecting the angular disposition of saidhousing in a second plane perpendicular to said first plane; electricalmeans for scanning each of said units to determine the angulardisposition of such respective units relative to a fixed reference andfor generating output signals indicative of the angular relationshipbetween the disposition of such units and the fixed reference; and meansfor electrically receiving and storing said output signals to makesubsequent calculations based thereon determinative of the orientationof said housing and borehole in relation to the earth''s surface.
 9. Amethod of determining the positional attitude of a borehole comprisingthe steps of: passing an instrument housing into the borehole on asingle conductor cable; measuring a parameter of the inclination of suchhousing in a first plane; measuring a parameter of the inclination ofsuch housing in a second plane; detecting a parameter of the directionof inclination of such housing in a borehole; providing signalsindicative of such parameters to the earth''s surface over the singleconductor cable; combining the parameters of inclination in relation tothe planes of measurement; and applying such parameter of direction tothe combined parameters of inclination to determine the true positionalattitude of such borehole.
 10. The method of claim 9 and furtherincluding the steps of providing pulses in timed proportion to themeasured parameters counting such pulses, storing data indicative ofsuch counted pulses, and transmitting such stored data to the surfaceprior to combining and applying such parameters.